1. Field of the Invention
This invention relates to a thermal transfer printer for color printing and, in particular, to a thermal transfer printer for color printing on a recording paper by using an ink sheet having sequential segments of ink of three primary colors or four colors including black.
2. Description of the Prior Art
A thermal transfer printer used as an output printer in the computer system, word-processor, and the like is readily capable of color printing the application of ink of several different colors to the same page of the same printing medium. Thus, such a printer can be used for outputting such data as displayed by the so-called computer graphics or to produce multi-color images.
A thermal transfer printer capable of color printing as described above has been disclosed in, for example, the Japanese Patent, Laid-open No. 58-140266 (1983).
In the thermal transfer printer such as above, generally, an ink sheet having sequential segments of ink in four colors including three primary colors (yellow, magenta, and cyan) and black and a recording paper are put one upon another and carried to a contact position between a thermal transfer head and the platen so that all colors of ink are thermally transferred to the recording paper in succession. Each time that printing in one color is completed, the recording paper is reversed, then brought forward and again printed in the succeeding color on the same page as that previously printed, the repeat of such process providing multi-color printing.
However, with a thermal transfer printer of this type, it is necessary to press a thermal transfer head to a platen or release the thermal transfer head from the platen very frequently in comparison with a usual printer. In such prior art printers, the head is pressed to the platen when a recording paper is first set on the printer to carry out the initial position setting of the recording paper relative to the thermal transfer head and then a predetermined color of an ink sheet is set to a printing position or when the recording paper is carried in the backward direction after completing the printing with an ink of one color.
However, with the above described conventional example, the mechanism comprises a first lever for pressing the thermal transfer head to the platen by a biasing force of a spring and a second lever for releasing the thermal transfer head from the platen by the action of an electro-magnetic solenoid. Accordingly, with such the conventional construction, the construction itself is complicated and the size and weight of each lever and the like is large, so that it is difficult to reduce the size of the printer as a whole and the printer has problems with respect to reliability and durability.
In addition, since the positional relation between the thermal transfer head and the platen is unstable directly after the printer is switched on, various kinds of problem occur in the subsequent controls. Accordingly, it is desired to instantly control the positional relation between the thermal transfer head and the platen to the predetermined initial condition when the printer is initially powered and carry out the subsequent controls with this initial condition as a basic state for control.
This is accomplished by the provision of mechanisms for pressing the thermal transfer head to the platen and releasing the thermal transfer head from the platen with a very simple structure of reduced size and weight, being more economical to produce and of a high reliability and durability.